Coated articles are known in the art for use in window applications such as insulating glass (IG) window units, vehicle windows, monolithic windows, and/or the like.
Conventional low-E coatings are disclosed, for example and without limitation, in U.S. Pat. Nos. 6,576,349, 9,212,417, 9,297,197, 7,390,572, 7,153,579, and 9,403,345, the disclosures of which are hereby incorporated herein by reference.
Certain low-E coating utilize at least one transparent dielectric layer of titanium oxide (e.g., TiO2), which has a high refractive index (n), for antireflection and/or coloration purposes. See for example U.S. Pat. Nos. 9,212,417, 9,297,197, 7,390,572, 7,153,579, and 9,403,345. Although high refractive index dielectric materials such as TiO2 are known and used in low-E coatings, these materials are not thermally stable and are typically not heat stable after tempering process of about 650 C for 8 minutes, due to film crystallization (or change in crystallinity) in as-deposited or post-tempering state, which may in turn induce thermal or lattice stress on adjacent layers in the film stack. Such stress can further cause change in physical or material properties of the stack and hence impact on the Ag layer, which results in deteriorated low E stack performance. Moreover, TiO2 dielectric layers in low-E coatings suffer from having a very low deposition rate during sputter-deposition of low-E coatings, thereby leading to significantly high costs associated with making low-E coatings.
Example embodiments of this invention solve these problems by providing a high index (high refractive index value n, measured at 550 nm) and low absorption (low k value, measured at 400 nm) hafnium (Hf) inclusive nitrided dielectric layer for use in low-E coatings. Unlike TiO2 dielectric layers, the high index hafnium inclusive dielectric layers herein have been found to be heat treatable so as to be substantially thermally stable upon heat treatment (HT), and can be sputter-deposited at much higher sputter-deposition rates than can TiO2. In certain example embodiments, the hafnium inclusive high index nitrided dielectric layer(s) may be of or include one or more of HfSiAlN, HfZrSiAlN, HfSiN, HfAlN, and/or HfAlZrN. It has been found that adding Hf to ZrSiAlN for example allows widening of its band-gap, and thus lowers considerably the optical absorption (k) while having a high refractive index (n). The same applies to adding Hf to ZrSiN, SiN and SiAlN in certain example embodiments. These materials have also been found to be heat stable (e.g., the variation of refractive index n may be no greater than 0.1 due to HT such as thermal tempering at about 650° C.). In certain example embodiments, it has been found that using a Hf inclusive dielectric layer (instead of a TiO2 dielectric layer) surprisingly results in an increase in visible transmission for the coated article. In certain example embodiments, the low-E coating may be used in applications such as monolithic or insulating glass (IG) window units, vehicle windows, or the like. While Hf inclusive high index nitrided dielectric layers discussed herein are preferably used in low-E coatings, this invention is not so limited and these layers may be used in other thin film coatings such as for high index layers in antireflective (AR) coatings.
“Heat treatment” (HT) and like terms such as “heat treating” and “heat treated”, such as thermal tempering, heat strengthening, and/or heat bending, as used herein means heat treating the glass substrate and coating thereon at temperature of at least 580 degrees C. for at least 5 minutes. An example heat treatment is heat treating at temperature of about 600-650 degrees C. for at least 8 minutes.
In an example embodiment of this invention, there is provided a coated article including a coating supported by a glass substrate, the coating comprising: a first dielectric layer on the glass substrate; an infrared (IR) reflecting layer comprising silver on the glass substrate, located over at least the first dielectric layer; a second dielectric layer on the glass substrate, located over at least the IR reflecting layer; and wherein at least one of the first and second dielectric layers comprises a nitride of hafnium (Hf), contains from 0-10% oxygen (atomic %), has a refractive index (n) of at least 2.21 at 550 nm, and further comprises at least one of Zr, Si, and Al.
In another example embodiment of this invention, there is provided a coated article including a coating supported by a glass substrate, the coating comprising: a first dielectric layer on the glass substrate; an infrared (IR) reflecting layer on the glass substrate, located over at least the first dielectric layer; a second dielectric layer on the glass substrate, located over at least the IR reflecting layer; a third dielectric layer on the glass substrate and located over at least the first and second dielectric layers; and wherein at least one of the first and second dielectric layers comprises a nitride of hafnium (Hf), and further comprises at least one of Zr, Si, and Al.